Computer tomography (CT) is a method of medical imaging. Here the spatial density distribution of an object, as a rule of a patient, is reconstructed from a series of two-dimensional projection images. The projection images are thereby acquired from different angles of view with a scanner apparatus comprising x-ray source and x-ray-sensitive detector. In order to reconstruct object density distribution with a high level of quality, it is necessary to know the precise position and orientation of x-ray source and detector.
In computer tomography both tube-like systems (computer tomographs) and also C-arm devices are known. Here the x-ray source is moved in a circular scan path around the object to be represented, while the detector is arranged in opposition to it. The reconstruction of the image data takes place on the basis of algorithms, which are adjusted according to the exact scan path of the x-ray source and the detector.
In order to guarantee or improve access to the patient during the x-ray procedure, scanner systems are called for whose x-ray source and detector are mounted on individually actuatable moving arms. These are for example moved in a motorized manner with the aid of rails and joints and thus have a high degree of freedom in their movement. General mechanical inaccuracies arise hereby, which lead to imprecise geometric data. Imprecise geometric data in turn results in image artifacts in the reconstruction result. If the mechanical inaccuracies mount up as a result of a multiplicity of actuation steps of the movement, this can result in the object to be represented no longer being capable of reconstruction.